The purine derivative of formula (I), hereinafter referred to as “compound (I)”, was first disclosed in the specification of WO 2008/122767 in the name Cyclacel Limited.

Studies have demonstrated that compound (I), having the chemical name (2R,3S)-3-(6-((4,6-dimethylpyridin-3-ylmethylamino)-9-isopropyl-9H-purin-2-ylamino)pentan-2-ol, exhibits potent CDK inhibitory activity and thus has potential therapeutic applications in the treatment of proliferative disorders, immune-mediated and inflammatory disorders, autoimmune and autoimmune-mediated disorders, kidney disorders, cardiovascular disorders, ophthalmic disorders, neurodegenerative disorders, psychiatric disorders, viral disorders, metabolic disorders and respiratory disorders.
Advantageously, compound (I) displays surprisingly high potency in cellular toxicity studies in a range of different cell lines.
The present invention seeks to provide compound (I) in crystalline form. In particular, the invention seeks to provide crystalline forms that retain the desired pharmacological activity of the compound. More specifically, but not exclusively, the present invention seeks to provide crystalline forms of compound (I) that exhibit one or more improved properties over the amorphous form.